Porphyrins XVII. Vapor Absorption Spectra and Redox Reactions: Tetraphenyl-porphins and Porphin
Edwards, L., David Dolphin, Gouterman, M., and Adler, A.D.
J. Mol. Spectrosc.
Vapor absorption in the range 800-200 nm are given for porphin, free-base tetraphenylporphin (H2TPP), and the Mg, Cr(III), Mn(III), Fe(III), Co, Ni, Cu, Zn, Cd, Sn(IV), and PbTPP complexes. Electronic bands Q, B, and M characteristic of the ring are found in the regions 540 nm (18,500 cm-1 ), 405 (24,700), and 205 (48,800). The region between the B and the M shows rather unstructured absorption, an order of magnitude less intense than the B region. Based on spectroscopic measurements, the ΔH of vaporization and abs. vapor pressures are calculated. The pressures averaged to approximately0.05 torr at 390 oC. Vacuum uv spectra of H2 TPP, NiTPP, CuTPP, and ZnTPP down to 145 nm are presented which show absorption across the entire range with more intense bands at 185 nm (54,000 cm-1 ), 164 (61,000), and 150 (67,000), and no evidence by Rydberg structure. The vapors of Cr, Mn, Fe, and Sn complexes show unusually different spectra from their solutions. Spectral change on electrolytic reduction establish that in the Mn, Fe, and Sn cases the vapors are those of the divalent metal. Solution spectra of H 2TPP, CuTPP, and FeClTPP were studied at 300 o C. Broadening comparable to the vapor spectra is observed. Also the visible bands shift to the red while the Soret band shows no change.